The use of gas abrasive in the dental industry has considerably reduced the pain and general unpleasantness involved in dental procedures. Traditional gas abrasive delivery systems worked much like a salt shaker. They were basically chambers which would be vibrated in order to force the abrasive out of the holes at the bottom of the chamber. Another type of gas abrasive delivery system vibrated the abrasive to flow up through a circular track to bring sand up through the top of the chamber. These systems had the common problem of excessive noise and vibration. Systems can be found which avoid the excessive noise and vibration by blowing gas over the top of the abrasive to create a dust cloud which could be blown or sucked out to the end piece. These systems had severe difficulty with abrasive flow control. The apparatus of this invention provides a gas abrasive delivery system having a more consistent flow pattern of the gas/abrasive stream. Also provided is a unique double-action pinch valve for controlling the flow of the gas/abrasive stream.